Magnetic toy building blocks



Feb. 10, 1959 c. CRONBERGER 2,872,754

MAGNETIC TOY BUILDING BLOCKS Filed July 2 8, 1955 2 Sheets-Sheet 1 lg i \ E I 30 T I I '3- FIG 5 2; .25 u L I (J I E T .20 U a 4 I .l 5 J 3 S i 'l I I 6 I x -3 -4 .5 .7

GAP E $22222 INVENTOR LUTHER 0. ORONBERGER Nmm m 1959 c. CRONBERGER 2,872,754

MAGNETIC TOY BUILDING BLOCKS Filed July 28, 1955 2 SheetsSheet 2 I00 1 g x O FIG 6 AIR GAP UNGHES)" FIG. 7

INVENTOR LUTHER C. GRONBERGER BY KW United States Patent This invention refers to magnetic toy building blocks and this application is a continuation-in-part of my copending patent applications SenNo. 223,991 filed May 1,

1951 for Magnetic Toy Building Blocks and Magnetic Fasteners, now abandoned and Ser. No. 278,640 filed March 26, 1952 for Magnetic Fasteners, now U. S.

Patent 2,742,250.

' It is one object of the invention to provide toy building blocks wherein equal optimal attractive forces on all surfaces of the blocks are obtained with a minimum of magnetic material.

Another object of the invention is to provide magnetic toy building blocks having equal attractive forces on all surfaces thereof, in which blocks the ratio of the main fluxes to the leakage fluxes is small and which blocks produce optimal attractive forces. 1 s

Another object of this invention isto provide magnetic toybuilding blocks having a high attractive eificiency.

Another object of the. invention is to provide magnetic toy. building blocks which are easy and. inexpensive to manufacture and the weight of which is light for a given size and for a given attractive force.

Still another object of the invention is to provide magnetic toy building blocks of a predetermined size wherein predetermined attractive forces are achieved with a minimum volume of magnetic material, thus minimizing cost and weight.

Further objects and advantages of the invention will become apparent as this specification proceeds.

The magnetic flux emanating from each magnet of a toy block consists of two components, the leakage flux and the main flux. The leakage flux is that portion of the total flux which passes through some object other than the toy block, including another toy building block, before re-entering the magnet at a pole of opposite polarity. The main flux passes from one magnet pole of a toy building block to another magnet pole thereof without reaching out into space and passing through a ferromagnetic object other than the particular toy block, and without attracting such object to the particular toy building block. Thus the main flux does not contribute to the attractive power or force of a magnetic toy-building block. The invention provides magnetic toy building blocks wherein relatively small permanent bar magnets are arranged in such a way that the attractive forces on all sides of the block are substantially equal and that the main flux is minimized while the leakage flux is maximized and assumes a considerable portion of the total flux.

For a better understanding of the invention reference may be had to the accompanying drawings wherein Fig, 1 is an isometric view of a toy building block embo ying the invention, I

.- Fig.2 is an isometric view of a corner region of another toy building block showing a modification of the i toy buildingblgck of the type partially shown in Fig. 2,

. and eight corners.

"ice

illustrates how such a fastener can be applied to magnetic toy building blocks of the type shown in Figs. 2 to 4, inclusive.

Referring now to the drawing, and more particularly to Fig. 1 thereof, reference numeral 1 has been applied to indicate a supporting structure of non-magnetic material substantially in the shape of a prism having six sides Reference numeral 2 has been applied to indicate the edges of supporting structure 1. This structure may consist of wood or of a suitable plastic, e. g. a phenolic resin. Supporting structure 1 is provided with four grooves or recesses G for accommodating bar magnets. Each of these recesses G extends from the bottom surface to the top surface of supporting structure 1 and is square in cross-section. The structure shown in Fig. 1 comprises four bar magnets, each accommodated in one of said four recesses G in such a way as to establish a magnet pole immediately adjacent to each of the eight corners of supporting structure 1, and to form a cyclic pattern of magnet poles of alternating polarity on each of the six sides of supporting structure 1. Considering, for instance, the front surface of the block as shown in Fig. 1, when following edges 2 in clockwise or counterclockwise direction, a cyclic pattern N, S, N, S of four magnet poles of alternating polarity can be ascertained. Such a pattern is present on all six surfaces of supporting structure 1.

For a better understanding of the invention it is necessary to define What a leakage gap versus pull gap curve is understood to be.

Consider a family of supporting structures identical to that of Fig. 1, of which all members are in the shape of a cube and differ only in regard to the length of the leakage gap thereof, i. e. in regard to the shortest distance L between poles of opposite polarity, or the spacing of poles N and S. The pull gap of each member of such a family of blocks is the longest 'gap filled with nonmagnetic material that can be formed between one side of the respective member and a given ferromagnetic test weight at which the test weight can barely be supported by? the respective member or, in other words, at which the test weight is held in equilibrium by the magnetic forces of the respective member and those of gravity. The pull gap so defined and so determined is an exact measure for the attractive power of a given block and is indicative of the most desirable range of leakage gaps.

In Fig. 5 pull gap lengths in inches have been plotted against the leakage gap lengths in inches for the arrangement of parts shown in Fig. 1. It is immediately apparent from Fig. 5 that the pull gap versus leakage gap curve has a critical optimum region. It is most desirable that the spacing between bar magnets N, S be so large as to establish leakage gaps between the poles situated immediately adjacent the eight corners of the block sufficiently large to cause operation of the block at the peak region of the pull gap versus leakage gap curve thereof. Good results will still be obtained with leakage gaps which are so large as to cause operation of the block above the lower third, preferably in the upper of the pull gap versus leakage gap curve thereof.

The table below indicates data derived from actual tests with a family of blocks of the above referred to kind having identical permanent magnets and leakage gaps of varying length.

Leakage gap, in.: Pull gap, in.

While it is more convenient to express the attractive power of magnetic toy building blocks in terms of pull gap length, their attractive power can also be expressed, if desired, in terms of weight actually pulled. To this end reference may be had to so-called pull curves showing air gap, e. g. in inches, against pull, e. g. in grams. In this context air gap means the distance between the pole of a permanent magnet attracting a ferromagnetic object and the ferromagnetic object attracted. Two such pull curves-each for a different magnetic material-have been shown in Fig. -6, one being designated by the reference letter X and the other by the reference letter Y. Reference to such a curve with its non-linear relation between pull in grams (or ounces) and air gap width in inches brings out the great importance of the correct choice of the width of the leakage gap on the attractive force of a toy building block.

Considering the relative proportions of the non-magnetic supporting structure 1 and of the permanent bar magnets N, S, it is apparent that a relative reduction of the size or cross-sectional area of each of the four permanent bar magnets N, S tends to reduce the attractive force of the building blocks. On the other hand, a relative reduction of size or cross-sectional'area of the four permanent bar magnets N, S tends to increase the pole spacing and thus the leakage gap, and to increase the ratio of leakage flux to main flux, and consequently increase the attractive .force of the building block. More generally speaking, in the structure of Fig. 1 any change of the cross-sectional area of the permanent magnets tends to have opposite effects upon the attractive forces of the block. The actual change of the attractive forces caused by any change of the cross-sectional area of the permanent magnets is the resultant of the two above referred-to opposite tendencies. It is thus possible to greatly reduce magnet size and yet obtain considerable attractive forces by virtue of concomitant increase of leakage gap length. In other words, it is possible to'substitute for the'relatively substantial permanent bar magnets shown in Fig. 1 bar magnets of greatly reduced size without decreasing the attractive power of the blocks below the desired level. Figs. 2, 3 and 4 which will be described below in detail refer to building blocks wherein thin wire-like rods of magnetic material have been substituted for the relatively heavy permanent bar magnets N, S of Fig. 1.

Regarding the relative size of the non-magnetic supporting structure and of the bar magnets, it is imperative that the cross-sectional area of bar magnets intended to be associated with supporting structures substantially in the shape of a cube be considerably less than A of the area of one side thereof. 'Where the supporting structure is in the shape of a prism rather than in the shape of a cube, the cross-sectional area of each of the permanent magnets ought to be substantially less than A of the area of the smallest side of the prism. Provided that the attractive forces are increased as much as possible by judicious choice of the leakage gap length, sufiicient attractive power can be obtained by means of permanent bar magnets whose cross-sectional area is even less than of the smallest area of one side, i. e. the smallest side, of the supporting structure. Figs. 2

to'4 illustrate a toy building block wherein high, perfectly equalized attractive forces have been achieved on all sides thereof in spite of drastic economy in expensive magnetic material.

Referring now to Figs. 2 to 4, supporting structure 1 of non-magnetic material, e. g. wood, is either in the Shape of a prism having six sides and eight corners, or in the shape of a cube. Supporting structure 1' is provided with eight recesses 4 for accommodating bar magnets therein. Each of the eight recesses 4 extends from one of the eight corners of supporting structure 1' generally toward the center C thereof. Center C is the geometrical center of the supporting structure as well as its center of gravity. Each of the recesses 4 encloses an acute angle with three of the six sides of the prismatic supporting structure 1.

The structure of Figs. 2 to 4 comprises eight permanent bar magnets N, S taking the place of the four permanent bar magnets N, S of the structure of Fig. 1. It will be apparent that the arrangement of magnets shown in Figs. 2 to 4 is the equivalent of the arrangement of magnets shown in Fig. 1 inasmuch as in the first mentioned figures pairs of serially related magnets take the place of one single magnet in the last mentioned figure. In the structure of Figs. 2 to 4 there is a considerable main flux between the poles of the mag nets which are situated within rather than immediately adjacent to the surface of supporting structure 1. This main flux is the equivalent of the flux within each of the permanent magnets N, S of Fig. 1 at a point situated between the north pole and the south pole thereof.

The poles N, S of the permanent magnets N, S which are situated immediately adjacent the corners of supporting structure 1 are spaced as far apart as the size of supporting structure 1' permits. This is conducive to a high leakage flux, a high ratio of leakage flux to .mainflux, and permits operation at a favorable point of the pull gap versus leakage gap characteristic of the structure.

It is apparent from the foregoing that all that has been said with regard to thestructure of Fig. 1 is;generally applicable to the structure of Figs. 2 to 4. Thus the type of .curve shown in Fig. 5 applies to the structure of Fig. 1 as well as to that of Figs. 2 to 4. The cross-sectional area of the eight permanent bar magnets N, S of the structure of Figs. 2 to 4, inclusive, ought to be considerably less than of the area of the smallest of the sixsides of supporting structure 1' if the latter is in the form of a prism, and may be even less than ,4 of that area.

The arrangement of the eight recesses 4 and of the eight permanent bar magnets N, S in the structure 'of Figs. 2 to 4 makes it much easier to secure the permanent bar magnets N, S to the supporting structure 1 than in the arrangement shown in Fig. 1. One simple way of securing the permanent bar magnets N, S in the recesses 4 is by means of cement.

Since the cross-sectional area of the permanent bar magnets N, S is very'small, it is desirable to provide the magnets N, S with pole pieces at the poles thereof situated at'the eight corners of the building block. This has been shown in Figs. 2 and 3 wherein reference numeral 3 has been applied to the pole pieces. These pole pieces 3 may be directly cemented to the supporting structure 1'. To this end the eight corners of the latter may be blunted, as indicated in Fig. 4, showing a building block without pole pieces comprising a supporting structure '1' having eight'blunted corners on which pole pieces may be afiixe'd, if desired. Figs. 2 and 3 refer to structures wherein the corner portions of "supporting structures 1' are blunted to facilitate the caps or pole pieces 3 of ferromagneticmaterial to be aflixed thereon.

If the permanent ba'r magnets N, S of the building closing the outer ends or orifices of the'recesse'sl in supporting structure 1, then it is possible to use the'pole pieces or caps for the purpose of securing each magnet N, S in the respective recess thereof, thus making it possible to entirely dispense with cement joints between the permanent magnets N, S and their supporting structure 1'.

Fig. 7 shows a magnetic fastener of the type disclosed in my above referred to co-pending patent application Ser. No. 278,640 and the way in which such a magnetic fastener can be applied to form magnetic toy building blocks of the kind shown in Figs. 2 to 4.

Referring now to Fig. 7, reference numeral 5 has been jumps axially outwardly into engagementwith cap 7 by virtue of the attractive force thereof, thus minimizing the reluctance of the magnet path between magnet N, S and cap 7. In other words, physical engagement of permanent bar magnet N, S and pole piece 7 is established by the magnetic action of bar magnet N, S only, i. e. without resorting to any auxiliary mechanical fastening means, such as adhesives, solder, etc., tending to increase the magnetic reluctance between the magnet proper and the polepiece thereof. Cap or pole piece 7 is concave at the inner side thereof. This is important in order to increase the reluctance of the magnet path between the outer and the inner pole of each magnet N, S which, in turn, is conducive to minimizing the main flux and to maximizing the leakage flux of each individual permanent magnet N, S. Cap or pole piece 7 engages the surface of block 6 only along the outer periphery 7 yet this limited area of contact is ample to establish a firm bond between cap or pole piece 7 and the surface of block 6. It is important not to fill the cavity 7 of cap or pole piece 7 with cement in order not to preclude magnet N, S from moving axially outwardly in recess 5 into engagement with cap 7 upon application of the latter to the surface of block 6.

It will be apparent that the arrangement of Fig. 7 lends itself particularly Well to providing the eight attractive magnetic units for the structure of Figs. 2 to 4, inclusive. The dash-and-dot line 8-8 in Fig. 7 indicates a corner region of a supporting structure such as that shown in Fig. 4 having eight blunted corner regions. Cap 7 covers one of these corner regions and maintains the magnet N S securely in the position thereof.

The shape of the recesses 5 for receiving the permanent bar magnets N, S and the shape of the permanent eight permanent bar magnets each accommodated -in.one

of said eight recesses in such a way as to establish a magnet pole immediately adjacent each said eight corners and to form a cyclic pattern of magnetic poles of alternating polarity on each of said six sides, and the cross-sectional area of each of said eight bar magnets being considerably less than /4 of the cross-sectional areaof the smallest of said six sides.

2. A magnetic toy building block as specified in claim 1 wherein each of said eight recesses and each of said eight bar magnets is substantially cylindrical and wherein each of said eight recesses has an orifice closed by a cap securing one of said eight bar magnets in one of'said recesses, said cap consisting of a ferromagnetic material forming an enlarged pole surface for one of said eight bar magnets and being directly attached to said supporting structure.

3. A magnetic toy building block comprising a supporting structure of nonmagnetic material substantially in the shape of a prism having six sides and eight" corners, eight recesses in said structure for accommodating bar magnets therein, each of said eight recesses extending from one of said eight corners'inwardly into said structure and each enclosing an acute angle with three of said six sides,'eight permanent bar magnets each cemented into one of said eight recesses in such a way as to form, a cyclic pattern of magnet poles on each of said six sides of said structure, the cross-sectional area of each of said eight bar magnets being considerably less than A of the cross-sectional area bar magnets N, S may vary, yet both are preferably cylindrical. While various permanently magnetic materials may be used for making magnetic toy building blocks embodying this invention, I prefer to use magnetic materials known as Alnico, or materials having like magnetic properties.

Although I have shown and described specific structures it is to be understood that the same were merely for the purpose of illustration and that changes and modifications may readily be made herein by those skilled in the art without departing from the spirit and scope of the appended claims.

I claim as my invention:

1. A magnetic toy building block comprising a supporting structure of non-magnetic material substantially in the shape of a prism having six sides and eight corners, eight recesses in said structure for accommodating bar magnets therein, each of said eight recesses extending from one of said corners inwardly into said structure and each enclosing an acute angle with three of said six sides,

of the smallest of said six sides and each of'said eight bar magnets being provided adjacent the outer pole thereof with a cap of ferromagnetic material forming a pole piece of enlarged area directly attached to said structure.

4. A magnetic toy building block comprising a supporting structure of non-magnetic material substantially in. the shape of a prism having six sides and eight corners, eight recesses in said structure each having an orifice for insertion therein of a magnet and each extending from one of said corners inwardly into said struc-' ture, eight permanent bar magnets eachaccommodated in one of said recesses in such a way as to establish a magnet pole immediately adjacent each said eight corners and to form a cyclic pattern of magnet poles of alternating polarity on each said six sides, the cross-sectional area of each said bar magnets being less than of the area of the smallest of said six sides, and eight caps of ferromagnetic material closing said eight recesses, each of said eight caps forming a pole piece of enlarged area for one of said eight magnets and being directly secured to said structure.

5. A magnetic toy building block as specified in claim 4 wherein each of said eight bar magnets is loosely fitted into one of said eight recesses and wherein each of said eight caps of ferromagnetic material and one of said eight bar magnets are held in physical engagement by magnetic attraction only.

6. A magnetic toy building block comprising a supporting structure of non-magnetic material substantially in the shape of a prism having six sides and eight corners, eight permanent bar magnets each projecting from one of said eight corners into said structure in such a way as to enclose an acute angle with three of said six sides, said eight bar magnets being oriented to form with outer poles thereof a cyclic pattern of poles of alternating polarity on each of said six sides of said supporting structure.

7. A magnetic toy building block as specified in claim 6 wherein said eight corners of said supporting structure are blunted and wherein a cap of ferromagnetic material is directly atfixed to the blunted region of each of said corners.

8. A magnetic toy building block comprising a supporting structure of non-magnetic material substantially in the shape of a prism having six sides and eight corners, eight recesses in said structure for accommodating magnets therein, each of said eight recesses extending from onesstsaid eight comers inwardlyinto said structure,

eightperm'a'nent bar magnets one in each of'said eight recesses, said :eight bar magnets being oriented to form with the poles thereofsituated adjacent said eight corners a cyclic'pattern of poles of alternating polarity on each of said six sides, the cross-sectional area of each of said eight bar magnets being so small in comparison to the spacing of the poles thereof situated adjacent said eight corners as to establish leakage gaps therebetween sufficiently large to 'cause operation of said block in the peak region of the 'pull gap versus leakage gap curve.

netic sheet material each forming a pole piece for one of said eight magnets, each of said eight caps being convex on'the side thereof remote and concave on the side thereof adjacent saidsupporting structure and each of said eight caps being directly secured with the rim region thereof only'to said supporting structure maintaining one of said eight magnets in one of said eight recesses, one of each said eight caps and one of each said eight magnets being held in'phy'sical engagement by magnetic attraction only.

10. A magnetic toy building block comprising a supporting structure of non-magnetic material substantially in theshape ofe'a prism having sixsides and eight corners, eight recesses in-said structure for accommodating magnets therein,--each of said-eightrecesses extending from one of said corners inwardly intorsaid structure enclosing an acute angle-with three of said six sides, eight permanent bar magnets each loosely fitted into one of said eight recesses to enable movement therein in a direction longitudinally thereof, said eight magnets being oriented in such a manner as to form jointly a cyclic pattern of poles of alternating polarity on each of said six sides, the cross-sectional area of each of said plurality of magnets being so small in comparison to the spacing of the poles thereof situated immediately adjacent said eight corners as to establish leakage gaps between said poles causing operation of said block in the peak region of the pull gap versus leakage gap curve, and eight caps of ferromagnetic sheet material each forming a pole piece for one of said plurality of magnets, each of said eight caps being directly secured to said supporting structure and each maintaining one of said plurality of magnets in one of said plurality of recesses, one of each said eight caps and one of each said eight magnets being held in physical engagement by magnetic attraction only.

References Cited in the tile of this patent UNITED STATES PATENTS 242,821 Farmer June 14, 1881 1,236,234 Troje Aug. 7, 1917 2,448,692 Teetor Sept. 7, 1948 2,495,644 Rowley Jan. 24, 1950 2,607,157 Smith Aug. 19, 1952 

